It revolves around the date of a postings request and the date it was actioned. I've dug down through all the data, cross checking the history trail with the the dates showing on the transactions. I've stared at the code in 3 on line programs and a batch program.
About half an hour ago I realised that the request was placed on a Thursday (17th April, 2003) and it was actioned on a Wednesday (23rd). Fishing out an old diary confirmed that the 17th was the Thursday before Good Friday and that the Wednesday was the day the returned to work (local authorities have the Tuesday off too).
So, assuming they didn't run postings on the Thursday night, all is correct. The request would be processed by the next run which was on the following Wednesday.